Apparatus for measuring phase difference of periodic waves



June 10, 1952 H. A. POOLE, JR

S FOR MEASURING PHASE M1? v/S l i mw w/ im Zw Bly@ im M v V V /HARMQN BY Patented June 10, 1952 .STAT Es APPARATUS FORMEASURfING rlHA-SE DIE-- 'FER/ENCE .OF PERIODI() `SVAYES HarmonA. P oolcLJr, Litchfield, Conn.; assigner to Bendix Aviation Corporation; Teterborm .,a corporation of Delaware .Application my :28, 195o, serial ,2N-.0. mensa The invention rrelates ato :the f measurement of 411a-hasedifference lbetween .fa Vpair ofi'recorded 'periodic waves, and more particularly .to .afdevice fformaking-suchtmeasurement .In lconvertingirecorded .electrical response of v :a .servo .for other device to vBode or ,Nyquist plots tfor fanalysis, it is :necessary "to :determinefthe phase dierence of the input and :output waves 'of .the 1. device at 1 various frequencies. `The :input vand'foutput waves usuallyarefrecorded on :ia `,trapt Another object is :to :provide apparatus afor :measuring the relative mhasesflofa nairof symmetric or non-symmetric recorded waves.

:Another @.obiect .sj 'to :provide agaparatnsv Yfor reading adrectlyithe .fre1ative--y phases jof ;a .fpar of irecordedcperiodicewavesavithcut makinganyscal- =.c.ulations.

- I-he i invention G0,ntemplates v a measuring decvice, fior determining gtheh .relative .phases of a pair u of A,periodic .wavesrecorded about -..a fp .air mf null lines. The device includesareferencemember having a reference lnegadaptedto .beinosi- .tionedin registery with .the'fnullpline KYoifone of the :waves .A.s1ide memberxis slidable .perpen- -.dictilarly to the reference ...line 71.rela'tive' ',.to .the

.f freecezmembewndhaetten@ argirfflines 1disposedatiapredeterminedangletofonezanother, ...andf.has V. a .series :of .lines .converging .at a point. Qne roi the .xn embers has a .center line disposed .bisectime anglefandrto l, passthrongh ,the cpoint and V@he Point isi-spaced @10mg the @enter Jin@ @from he.. :of the angle afdisianeeqgl to Ythe .distance between ..the null. .lines of the .re- :grdedlilrieslig .vivevesl .,-A Seeleecalibratediin :.angla'rf measurements forear .be wedged. :with .thepnveiggingdines. .The.r measuring device fused. .te perform :method Arf, determining. the :ph-ase; @meterme between two recorded waves. The :.niethodfeomprises Plating 1a.. devi wf, the., fknd s.descrilved .i21 claims.

' ,2 .relative to .the recorded wavesl so .that 'the :refterence .linelon .the reference'member is aligned wt'h'a nullline. Thedevice is movedalong the null `line until the center 'line on the .device extends through .a null on oneof .the waves. The .slide member of Athe device is Mmoved 4perperl- .dicularly to the null lines relative to 'the .refer- .ence member ,until .the converging lines ron Vthe slide' member :pass through a `pair .of hulls on 1o theorie wave. The angular measurement ofthe converging line .passing through .the null of ithe other .wave .corresponding to .the .rstmentioned nullv of l ..the lone :wave vis .readon the vangular .measvuringscale.A

l5 The foregoing f and .other ,objects .and .advantages vof the vinvention .will appear more 'fully hereinafter ,from `a consideration of the detailed description `which vfollows, Itaken together .with the accompanying .drawing v.wherein .one embodi-` 20 vment .of .the invention is illustrated. It t be expresslyunderstood however, that the drawing is .for the .purposes of illustration .and description.only, Jandiis vnot to be construedas dening ...the limitsothe invention.

l2,5v `AIn .thedrawingEigure 1 is a plan View of .a

.novel .device constructed -according to' the invention for indicating the relative phases of a -pair of `waves .recordedon .a .chart cina' two-.wave recorder.

.3,0 2 showsachartof va two-.wave recnrder .adap .ted r.for `use .with the novel device ...ofthe V*present,im/.vention .and .lhaving recorded thereon a pair of non-symmetric waves.

:Referring .now to .the drawing .for a :morefde- ..35 Atailedl'des,criloizionof'the novelfdevicefofthe Ipresent .invention `for Vmeasuring .the relative phases of fa pairof .recorded waves, vthe device isshwn in Figure .1, Las .comprising a reference member l having -a 7pair of parallellines/S, 5 extending A0 j lengthwsefthereof. A slide member l1 .isIsld- .ably ,mounted .on reference member .l' formolve- ,ment y.transversely Ythereof ,and yperpendcnlarly Ato parallel .lines 3, .5. The reference member .and slide member .may beheld together biffa 14,5 dovetailed connection -o`r in .any `other .suitable .mannen .A1-Deir .0f visosceles triangles 9, .Il `are drawn .fon.s'1idei.member1 andthe .triangles have-. .a .common .baseline i3 .extending parallel .to .lines Thebase of {eaeh .triangley. isfeq-ual to .its height. as .measured'-along .a center jline vl5, extending .lengthwise of slide member mld perpendicular 4r.to base line lf3 VAand .to gparallellines, .5. -;'I"i'1e.sidesY .|1, .|.9.of;.tr .i

@55 angle' 9 are disposed at an angle 0 andthe sides 2I, 23 of triangle II parallel to sides I1, I9 converge at an angle With this arrangement, angle and angle qa equal 53 degrees 8 minutes. Center line I bisects angles 0 and fp and the apex of angle 0 is spaced from the apex of angle along center line I5 a distancel equal to the distance between parallel lines 3 and 5. A series of degree lines converge at the apex of angle qs and are spaced equally along base line I3 at each side of center line I5 between sides 2! 23 of triangle I Il and are calibrated proportionately in degrees, center line I5 being marked zero degrees and sides 2|, 23 being marked 180 degrees. To avoid parallax in adjusting the device to a chart, as described below, slide member I preferably is positioned directly adjacent the chart and the lines are ruled on the sides of the slide member and the reference member adjacent the chart. The device may be used for measuring the phase difference of a pair of recorded symmetric periodic waves including an output wave 21 and a reference wave 29 of the kind shown in Figure 1 by positioning reference member I so that lines 3, 5 are in registry with null lines 28, 3S of the chart. The device is moved lengthwise along the null lines until center line I5 on slide member 1 passes through a null point, such as 5 I, of reference wave 29. Slide member 1 is moved perpendicularly to center lines 3, 5 until the outer sides I1, I9 of triangle 9 pass through null points 33, 35 of reference wave 29 adjacent null point 3|. The portion of reference wave between null points 33, corresponds to a singlecycle. The phase difference may be read directly on the device on the degree scale at base line IBof triangle II by noting Vthe radial degree line 25 which passes through null point 31 of output Wave 21 corresponding to null point 3l .on reference wave 25. If none of the linesv pass directly through null point 31 of output wave 21, the angle may be determined by linear interpolation along reference line 3. Whether the phase of the output wave leads or lags the reference wave is determined by the direction of motion of the tape on which the waves are recorded as it passes through the recorder and by the position of the null of the output wave relative to center line I5.

The device may be used also to determine phase difference between a pure sine reference wave and a non-symmetric periodic output wave by taking readings on the scale in the manner described for two successive nulls on the output wave and then averaging the readings.

Ihe device may be used also to determine the phase shift of a non-symmetric output wave 39 relative to -an identical non-symmetric reference wave 4I as shown in Figure 2. The device may be used in either of two methods to accomplish this end. In both methods, reference member I is 'positionedon the chart so that parallel lines 3, 5

are in registry with null lines 43, i5 of the chart.

In one method, the device is moved lengthwise along null lines 3, 45 and slide member 1 is moved perpendicularly to the null lines until sides I1, I9 of triangle 9 pass through null points, such as 41, 49, defining a single cycle of the reference wave.Y The device then is moved lengthwise of the null lines until center line I5 passes through null point 5I of the cycle defined'by null points 41, 49. The phase difference between output wave 39 and reference Wave 4I may be read` directly on the device fromV the radial degree line 25 which passes through the corresponding null point 53 of the Youtputwave or Vby linear interpolationalongv null line 43. Y'

The second method comprises moving the device lengthwise of null lines 43, d5 until center line I5 passes through null point 5I Slide member 1 is moved relative to reference member I transversely of null lines 43, 45 until sides I1, I9 of triangle S pass through null points 51, 5i) of the reference wave defining two complete cycles, one at each side of null point 5 I. The phase diiference between the reference wave and the output wave may be read on the degree scale by doubling the reading of the degree line 25 extending through null point 53 on output wave 39 or by interpolating linearly along null line [13. Likewise, the phase difference may be obtained by usingk any other even number of complete cycles instead of two as described above. In this case, the reading is multiplied by the number of complete cycles used.

'I'he device and method described facilitate determining the phase difference between a pair of recorded periodic waves and avoids the tediousness of the methods used heretofore. While no mechanism has been shown for sliding slide meme. ber 'l relative to reference member I, it may be desirable to use gearing or any other suitable means to provide for accurately positioning the slide member relative to the reference member in proper position on the chart.

It should be understood that lines I5, I1, I 9, 23 and 25 may be of any suitable length without actually completing triangles 9 and I! without af.- fecting the accuracy of the instrument. Also, the distance between the apex of angle 0 and the apex of angle c may be varied as determinedby the distance between the null lines on the chart.

When determining the phase difference between a pair of recorded waves with the device according to the several methods described, the device may be of transparent or semi-transparent material and be placed between the chart and the observer, or the device'may be of non-transparent material and placed on the side of the chart remote from the observer, whereupon the chart should be of transparent or semi-transparent material, such as thin paper. Also, it is immaterial whether the device is moved relative to the chart o1' whether the chart is moved relative to the device.

Although but one embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changesk can be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.`

Whatris claimed is:

1. In a device of thekind described for determining the relative phases of a pair of periodic Waves recorded about spaced parallel null lines, a reference member having a reference line adapted to .be positioned in registry with the null line of one of the Waves, a slide member slidable perpendicularly to said reference line relative to said reference member and having thereon a pair of lines disposed at a predetermined angle toV one another and having a series of lines converging at a point, one of said members having a center line disposed to bisect said angle and to pass through said point, and said point :being spaced along said center line vfrom the apex of said angle a; distance equal tothe distance between the null lines of the recorded periodic waves. A l l Y- 2. In a device of the kind described for deterasses-611 ativeto vsaid Vreference member and rhaving'thereoni a pair of lines'disposed at an angleof 53 degrees `8**minutes to one YanotherY and Ahaving-1a series kof lines yconverging ata point, one o'f said -membershaving a-'center linedisposed tobi/sect Athe `angle and "topass through said point, said point ybeing spaced along :said icenter 'line 'from the apex of said angle adistanceequalto 'the distance Ybetween thenull-'lines on the chart.

3. In a device of the kind described for determining the relative phases-of a pair of perifodichwavcs recorded von a chartiabout a pair of null lines, a reference member. `having a reference linev adapted to vbe positioned in registry with the null line of one of lthe Waves, a slide .member slidable perpendicularly to said refer- Yenice ine relative to Ysaid reference member vand 'having lthereon a pair of lines disposed v'atan angle of F53 degrees 8 minutes to one another and having 'a -series of lines lconverging ata '1`5o`int,'one` of Hsaid members having a center line disposed to bisect the angle and to pass through said point, said point being spaced along said center line from the apex of said angle a distance equal to the distance between the null lines on the chart, and a scale calibrated in angular measurements associated with said converging lines.

4. In a device of the kind described, a reference member having a pair of parallel lines thereon, and a slide member slidable perpendicularly to 4said parallel lines relative to said reference member and having thereon a pair of lines disposed at a predetermined angle to one another and having a series of lines converging at a point, one oi? said members having a center line disposed to bisect said angle and to pass through said point, and said point Ibeing spaced along said center line from the apex of said angle a distance equal to the distance between said parallel lines on said reference member, and a scale calibrated in angular measurements associated with said converging lines.

5. In a device of the kind described, a reference member having a pair of parallel lines thereon, and a slide member slidable perpendicularly to said parallel lines relative to said reference member and having thereon a pair of lines disposed at a lpredetermined angle to one another and having a series of lines converging at a point, one of the lines of said series being disposed to bisect said angle and to pass through said point, said point being spaced along said one line from the apex of said angle a distance equal to the distance between said parallel lines on said reference member, and a scale calibrated in angular measurements associated with said converging lines.

6. In a device of the kind described for determining the relative phases of a pair of periodic waves recorded about a pair of null lines, a reference member having a reference line adapted to be positioned in registry with the null line of one of the waves, and a slide member slidable perpendicularly tc said reference line relative to said reference member and having thereon a pair of lines disposed at an angle of 53 degrees 8 minutes to one another and having a series of lines converging at a point, a pair of the lines ci said series"beir ig parallel ito lsaidiother pair of lines, ione ci thellinesfofsaid :seriesbeingfdisposed to b'isec't said V-ang'le :and Ito pass :through said point, -saidfpoint 4being .spaced i'along `said 'one `line from itlfieiapex -o saidangle 'a `distance equal `to 'the Y distance `lbetweensaidnull lines, and

a -scale calibrated in degrees associated-withsaid converging lines, said pair Vof 'lines -fof vs'aid'serie's being-marked: 180. ldegrees :and said one line-noi -said series being marked/'zero :deg-rees, and fthe lremainder aci-Ethe lines of :said lseri'es'between said one 'line :and said :pair `of .lines 'of-.saidseries being calibrated in degrees proportionately.

i7. lIna .device/of thekind described .ifor determining the relative phases of;1a;pair..of periodic erence member having f'a :reference line adapted to libe positioned yinregistryfwith lthe .null :line fof Lone for the .'waves, .za Vslide member fslidable in La directionl zperpendicularly to saldi .reference .line

erelativeffto saidzreference member :and having thereon ran Kisosceles itri'angle :having a iba-se (equal :in length itc a center -linev perpendicular `to the base and ibisecting theangle "denjedby the zsides Vof 'the triangle,- .said :reference .member vhaving;a series'of lines thereon vconverging at ,ia-gpoinit .on said :center aline lspaced from the :apex of said :angle 'a distance `'equal to the Idistance ,between the null lines of the recorded waves, and said series of lines .being calibrated in angular measurements to facilitate reading the phase difference of the recorded waves. 4

8. In a device of the kind described, a reference member having a pair of parallel lines, and a slide member slidable perpendicularly to said parallel lines relative to said reference member and having thereon a pair of isosceles triangles, each having a base equal in length to a center line perpendicular to the base and bisecting the angle dened by the sides of the triangle, the sides of one triangle being parallel to the sides of the other triangle and the distance between the apeces of the angles of said triangles along said center line being equal to the distance between the parallel lines on said reference member, one of said triangles having a series of lines spaced equally along the base line and converging at the apex of the angle defined by the sides of the associated triangle.

9. In a device of the kind described, a reference member having a pair of parallel lines, and

a slide member slidable perpendicularly to said parallel lines relative to said reference member and having thereon a pair of isosceles triangles, each having a base equal in length to a center line perpendicular to the base and bisecting the angle defined by the sides of the triangle, the sides of one triangle being parallel to the sides of the other triangle and the distance between the apeces of the angles of said triangles along said center line being equal to the distance between the parallel lines on said reference member, one of said triangles having a series of lines spaced equally along the base line and converging at the apex of the angle dened by the sides of the associated triangle, and a scale calibrated in degrees along the base of the triangle and associated with said series of lines, said center line being marked zero degrees and the sides of the associated triangle being marked degrees.

10. In a device of the kind described for determining the relative phases of a pair of periodic Waves recorded about lspaced parallel null lines, a transparent reference member having a reference line adapted to be positioned in registry with 7 the null line of one of the waves, a transparent slide member slidable perpendicularly to said reference line relative to said reference member and having thereon a pair of lines disposed at a predetermined angle to one another and having a series of lines converging at a point within the* angle dened by said pair of lines, one of said members having a center line disposed to bisect said angle and to pass through said point, and said point being spaced along said center line from the apex of said angle a distance equal to the distance between theV null lines of the recorded periodic waves.

11. In a device of the kind described for determining the relative phasesof a pair of periodic waves recorded on a chart, a reference member having means for aligning said member in pre'- determined position relative to said chart, a member movable relative Yto said reference member and having thereon a pair of lines disposed at a predetermined angle toY one another and having a series of lines converging at a point, one of said members having a center line disposed to bisect said angle and to pass through said point,

and said point being spaced from the apex of said angle a distance equal to the distance between the loci of null points of the'waves.

. 12. In a device of the kind described for determining the relative phases of a pair of periodic waves recorded on a chart, a reference member having means for aligning said member in predetermined position relative to said chart, a member movable relative to said reference member and having thereon a pair of lines disposed at a predetermined angle to one another and having a series of lines converging at a point, and said point being spaced from the apex of said angle a distance equal to the distance between the loci of null points of the waves and being positioned relative to said angle so that a line drawn through said point and the apex of said angle bisects said angle.

HARMON A. POOLE, Jn.

-REFEREN CES CITED `The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,232,290 Grunberg v July 3, 1917 1,271,907 Jury July 9, 1918 1,416,519 Sparr May 16, 1922 1,930,478 Jones Oct. 17. 1933 2,088,533 Phelps July 27, 1937 

